Laryngeal mask airway size selection in males and females: ease of insertion, oropharyngeal leak pressure, pharyngeal mucosal pressures and anatomical position

We have compared ease of insertion, oropharyngeal leak pressure, directlymeasured pharyngeal mucosal pressure and anatomical position (assessedfibreoptically) for the size 4 and size 5 laryngeal mask airway (LMA) in 20male and 20 female patients. Microchip pressure sensors were attached tothe LMA at locations corresponding to the piriform fossa, hypopharynx, baseof the tongue, lateral and posterior pharynx, and the oropharynx.Oropharyngeal leak pressure, mucosal pressure and fibreoptic position wererecorded during inflation of the cuff from 0 to 30 ml in 10-ml increments.In males, oropharyngeal leak pressure over the inflation range was higherfor size 5 (21 vs 17 cm H2O; P = 0.01); mucosal pressure over the inflationrange was higher in the posterior pharynx for size 4 (7 vs 2 cm H2O; P =0.007), and higher in the piriform fossa (8 vs 5 cm H2O; P = 0.003) andhypopharynx (9 vs 5 cm H2O; P = 0.003) for size 5. In females,oropharyngeal leak pressure over the inflation range was the same (21 vs 21cm H2O), but mucosal pressure over the inflation range was higher in thepiriform fossa (21 vs 8 cm H2O; P = 0.003) and posterior pharynx (4 vs 2 cmH2O; P = 0.004) for size 4, and higher in the lateral pharynx (5 vs 1 cmH2O; P = 0.01) and oropharynx (11 vs 5 cm H2O; P = 0.009) for size 5. Thedistribution of mucosal pressure was different for size 4 between males andfemales, but not for size 5. For both males and females, fibreopticposition was similar. We conclude that the size 5 LMA is optimal in males,but either size is suitable for females. The shape of the pharynx may bedifferent between males and females.